Method of synthesizing metal -based composite material by melt reaction in coupling magnetic field and ultrasonic field

ABSTRACT

A method of synthesizing metal matrix composite material by melt reaction in coupling magnetic field and ultrasonic field comprises: adjusting metal-base melt to the onset reaction temperature after refining, then adding reactants which generate reinforced particles by in-situ synthesis reaction with melt, keeping the reacted melt stand until it is cooled to casting temperature after the reaction, and then casting. Magnetic field and high-energy ultrasonic field are exerted simultaneously during the reaction. The magnetic field can be high-power pulse magnetic filed, high-frequency oscillating magnetic field or low-frequency alternating magnetic field. The metal matrix composite material produced by the above-mentioned method exhibits that reinforced particles are much finer, more uniformly distributed, and fit with metal matrix better.

TECHNICAL FIELD

The invention relates to the technical field of novel composite materialsynthesis, in particular to a novel method of synthesizing particlereinforced metal matrix composite material by in-situ melt reaction incoupling electromagnetic field and ultrasonic field.

BACKGROUND ART

Particle reinforced metal matrix composite material has a wideapplication prospect in the fields of advanced electric and electronicdevices, aviation spacecrafts, machine, bridge tunnel engineering, etc.because of its excellent mechanical properties and physical and chemicalproperties owing to its composite structure and has been one of researchhotspots of metal matrix composite material in recent years. Presently,in-situ reaction synthesis method is the primary method of preparingparticle reinforced metal matrix composite material, its principle isthat alloying elements or compounds which can generate second phase areadded in metal matrix melt to produce in situ particle reinforcedcomposite material by generating particle phase by in-situ reaction withmetal melt at a certain temperature. Because of in situ formation ofparticle phase, the composite prepared by the method has clean bondinginterfaces between particles and metal matrix, good wettability and highbonding strength. However, the technique has a series of problems ofdifficult control of reaction process, easy growth even aggregation ofparticle phase, and uneven distribution.

External field can improve the thermodynamic and dynamic conditions ofin-situ synthesis reaction to promote the in-situ reaction andsimultaneously control over growth or segregated aggregation of particlephase. Therefore, in-situ synthesis of metal matrix composite materialin external field gets more and more attention from researchers. Chinesepatent CN 1676641A (Date of publication: 2005.10.5, Title: Magneticchemical reaction in-situ synthesizing method for preparing metal matrixnano composite material) provides a synthesis method by in-situmagnetic-chemical reaction in magnetic field (stable magnetic field,alternating magnetic field and pulsed magnetic field), the methoddisclosed by the patent has excellent effect in fining reinforcedparticles. Chinese patent CN 1958816 (Date of publication: 2007.05.09,Title: technique for preparing composite material of aluminum basedsurface enhanced by in situ particle through powered ultrasonic method)provides a technique for preparing in situ particle reinforced (Al₃Tiphase) aluminum based surface composite material through a poweredultrasonic method, causing reinforced phase to be distributed evenly inthe surface layer of matrix and interfaces to be bonded better.

However, the effect of exerting single electromagnetic field orultrasonic field on synthesizing particle reinforced composite materialby in-situ reaction is unsatisfied. When exerting single magnetic filed,the action intensity of the magnetic field in metal decays exponentiallydue to insurmountable skin effect of the electromagnetic field in metalmelt, and the effective depth of the electromagnetic field acting in themelt is limited, especially when employing a large-volume bath or anelectromagnetic field with higher frequency, the difference of theeffect of the electromagnetic field in the melt is significant, namely,the effect of the electromagnetic field in the melt shows severenonuniformity, the effect of the electromagnetic field is weak in thecentral area and strong at the edge area. When exerting singleultrasonic filed, because ultrasonic wave is mechanical sparse-densevibration wave which belongs to longitudinal wave, ultrasonic wave hasobvious directivity, and meanwhile, the ultrasonic wave also decaysseriously in metal melt, ultrasonic effect mainly concentrates in thecylindrical area under an amplitude transformer, namely, the effect ofthe ultrasonic field concentrates on the central area of the melt and isweak at the edge area of the melt.

In order to compensate the deficiencies of exerting singleelectromagnetic filed or ultrasonic field, the invention provides anovel method of in-situ synthesizing particle reinforced metal matrixcomposite material by coupling electromagnetic field and ultrasonicfield.

SUMMARY OF THE INVENTION

An aspect of the invention is to provide a method of synthesizing insitu particle reinforced metal matrix composite material by meltreaction in coupling magnetic field and ultrasonic field, which is usedfor preparing high-performance in-situ particle reinforced metal matrixcomposite material.

The basic principle of the invention lies in simultaneously exertingmagnetic field and high-energy ultrasonic field during synthesis ofin-situ particle reinforced metal matrix composite material, utilizingmagnetochemistry principle of magnetic field generating electromagneticforce, magnetization and eddy current induction heat in melt andsonochemistry principle of high-energy ultrasonic field generatingultrasonic cavitation and ultrasonic current impact to perform couplingduring synthesizing the composite material so as to achieve the goals ofcontrolling the distribution of particle phase, inhibiting the growthand aggregation of particles and changing the thermodynamic and dynamicconditions of in-situ synthesis reaction, thereby realizing thesynthesis of the particle reinforced metal matrix composite material bycoupling magnetochemistry of magnetic field and sonochemistry ofhigh-energy ultrasonic filed. The principle of the method is describedas follows by combining FIG. 1 to realize the scheme:

Composite material melt 2 is synthesized in a bath (or melting pot) 1made of thermal-insulating refractory material, a high-energy ultrasonicamplitude transformer 3 is inserted into the upper part of the bath (ormelting pot), the melt undergoes ultrasonic treatment, a magnetic field4 is exerted to the outer side of the bath (or melting pot). Themagnetic field can be exerted in different modes according topreparation methods of the composite material and effects required.Therefore, the exerted magnetic field can be high-power pulse magneticfiled, high-frequency oscillating magnetic field or low-frequencyalternating magnetic field.

The principle of coupling magnetic field and ultrasonic field is asfollows:

(1) The exerted magnetic field 4 is high-power pulse magnetic filed,namely, high-power pulse magnetic filed is coupled with ultrasonicfield. In the melt, the high-power pulse magnetic field generates apulse electromagnetic force, a pulse magnetizing force and joule heatproduced by induced current, which accelerates in-situ chemical reactionand disperses particle phase. However, the pulse magnetic filed decaysin a certain extent in the metal melt, and under the effect of themagnetic field, the reaction is strong at the edge area of the melt andweak at the central area, so the magnetic field shall be coupled withthe high-energy ultrasonic field which has powered supersonic generatingcavitation effect and acoustic streaming impact in the melt, wherein thecavitation effect controls the aggregation of particles, and theacoustic streaming impact plays a role of stirring in micro area.Because the effect of ultrasonic field is strong at the central area andweak at the edge area, the magnetic field and the ultrasonic field justcompensate for each other to accelerate in-situ reaction by coupling,achieving the goals of fast formation and dispersion of particle phase.

(2) The exerted magnetic field 4 can be high-frequency oscillatingmagnetic field which has skin effect in the melt and thus centrally actson the edge of the melt and generates an electromagnetic force toparticles in the composite material melt to control the aggregation ofthe particles. The ultrasonic field mainly acts on the middle area ofthe bath.

(3) The magnetic field 4 can be selected as low-frequency stirringmagnetic field coupling with power ultrasonic field if the requirementson size and distribution of particles of the composite material arelower. Especially when the amount of metal to be treated is large enoughto be in tons, because of the limitations of present high-frequencyoscillating magnetic field and high-power pulse magnetic field, couplinglow-power stirring magnetic field and high-energy ultrasonic field alsocan be adopted to obtain an ideal effect. The principle lies inhigh-energy ultrasonic field generating cavitation effect and acousticstreaming impact in the melt, wherein cavitation effect controls theaggregation of particles, and acoustic streaming impact plays a role ofstirring in micro area; the exerted low-frequency stirring magneticfield 4 performs electromagnetic stirring to the whole bath, so theultrasonic stirring effect is more obvious, and the local effect orconcentrated effect of ultrasonic treatment can be controlled.

On the basis of the principle the invention has the following schemes:

A method of synthesizing metal matrix composite material by meltreaction in coupling magnetic field and ultrasonic field comprises:adjusting metal-base melt to the onset reaction temperature afterrefining, then adding reactant powder which generates reinforcedparticle phase by in-situ synthesis reaction with melt, simultaneouslyexerting magnetic field and high-energy ultrasonic field during thesynthesis reaction, keeping the reacted melt stand until it is cooled tocasting temperature after reaction, and casting.

In the method of the invention, said exerted field can be high-powerpulse magnetic field, high-frequency oscillating magnetic field orlow-frequency alternating magnetic field. The invention has thefollowing three technical schemes according to different exertedmagnetic fields:

(1) Coupling high-power pulse magnetic field and high-energy ultrasonicfield

The range of electromagnetic parameters of high-power pulse magneticfield is as follows: pulse current frequency is 0.1 Hz-10 Hz, pulsecurrent density is 1 KA/m²-10 KA/m², charging voltage is 1 KV-20 kV, andcentral magnetic field intensity is 0.5-20T. Electromagnetic parameterscan be selected according to the size of the melting pot and the type ofthe melt, and the effect is remarkable if pulse magnetic field intensityin the melt is over 1T.

The frequency of ultrasonic field is 10 kHz-30 kHz, and ultrasonicintensity is 0.5 kW/m²-60 kW/m².

The specific steps comprise: adjusting metal-base melt to onset reactiontemperature after refining, then adding reagent which generates particlephase by in-situ reaction with the melt, turning on magnetic field,inserting an ultrasonic amplitude transformer below liquid level about5-6 mm after the magnetic field is stable, turning on an ultrasonicdevice, ultrasonic treatment time being 60 s-600 s, turning off theultrasonic device after time out, turning off the magnetic field,keeping the melt stand until it is cooled to the casting temperature,and casting.

The method is especially suitable for preparing metal matrix compositematerial with small amount and having extremely high requirement forperformance.

(2) Coupling high-frequency oscillating magnetic field and high-energyultrasonic field

The range of electromagnetic parameters of high-frequency oscillatingmagnetic field is as follows: high-frequency reference wave frequency is10 kHz-30 kHz, amplitude modulation oscillating wave frequency is 1Hz-30 Hz, power range is 0-100 kW, electromagnetic parameters can beadjusted according to the amount and type of melt, bath and stirringintensity, higher reference wave frequency is adopted for aluminum-basedor copper-based melt, lower reference wave frequency is suitable forFe-based, Ni-based or Zn-based melt, oscillating wave frequency isdetermined by the condition of stirring melt and related to thestructure of a reactor and the type of the metal melt, preferably thereis no strong turbulence in the melt.

The frequency of ultrasonic field is 10 kHz-30 kHz, and ultrasonicintensity is 0.5 kW/m²-60 kW/m².

The specific steps comprise: adjusting metal-base melt to the onsetreaction temperature after refining, then adding reactant powder whichgenerates reinforced particle phase by in-situ synthesis reaction withmelt, turning on magnetic field, inserting an ultrasonic amplitudetransformer below liquid level about 5-6 mm after the magnetic field isstable, turning on an ultrasonic device, ultrasonic treatment time being60 s-600 s, turning off the ultrasonic device after time out, turningoff the magnetic field, keeping the melt stand until it is cooled to thecasting temperature, and casting.

(3) Coupling low-frequency alternating magnetic field and high-energyultrasonic field The range of electromagnetic parameters oflow-frequency alternating magnetic field is as follows: frequency is 0.1Hz-60 Hz, working current is 1 A-10000 A, electromagnetic parameters canbe adjusted according to the amount and type of melt, bath and stirringintensity, higher frequency is adopted for aluminum-based orcopper-based melt, lower frequency is suitable for Fe-based, Ni-based orZn-based melt.

The frequency of ultrasonic field is 10 kHz-30 kHz, and ultrasonicintensity is 0.5 kW/m²-60 kW/m².

The specific steps comprise: adjusting metal-base melt to the onsetreaction temperature after refining, then adding reactant powder whichgenerates reinforced particle phase by in-situ synthesis reaction withmelt, turning on magnetic field, inserting an ultrasonic amplitudetransformer below liquid level about 5-6 mm after the magnetic field isstable, turning on an ultrasonic device, ultrasonic treatment time being60 s-600 s, turning off the ultrasonic device after time out, turningoff the magnetic field, keeping the melt stand until it is cooled to thecasting temperature, and casting.

Additional remarks: low-frequency alternating magnetic field can berotating stirring magnetic field or travelling wave stirring magneticfield within the above range of parameters, rotating stirring magneticfield is exerted on the side surface of the bath, or travelling wavemagnetic field is exerted on the bottom of the bath, the both belong tothe technical scheme of the invention.

The method can be used for small-batch production as well as large-scaleindustrial application.

The invention has the following advantages compared with the prior art:

(1) Because the composite material is synthesized by coupling magneticfield and ultrasonic field, the coupling of magnetic field andultrasonic field causes particles to be finer and uniformly distributed;

(2) Ultrasonic wave oscillating stirring and electromagnetic stirringimprove the dynamic conditions of synthesis, and particle phase fitswith metal matrix interface better; and

(3) Magnetochemistry cooperates with sonochemistry to improve thethermodynamic conditions of in-situ reaction, which accelerates thein-situ reaction speed and controls the growth of particle phase.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a device A used in the method of theinvention;

FIG. 2 is a schematic diagram of a device B used in the method of theinvention;

FIG. 3 is a schematic diagram of a device of an embodiment;

FIG. 4 is SEM images of particle reinforced Al matrix composite material(Al₃Zr_((s))+ZrB_(2(s))) prepared in coupling high-power pulse magneticfield and ultrasonic field in Embodiment 1;

FIG. 5 is SEM images of particle reinforced Al matrix composite material(Al₃Zr_((s))+ZrB_(2(s))) prepared in coupling high-frequency oscillatingmagnetic field and ultrasonic field in Embodiment 2; and

FIG. 6 is SEM images of particle reinforced Al matrix composite material(Al₃Zr_((s))+Al₂O_(3(s))) prepared in coupling low-frequency stirringmagnetic field and ultrasonic field in Embodiment 3.

Wherein, 1 is bath or melting pot made of thermal-insulating refractorymaterial; 2 is composite material melt; 3 is ultrasonic amplitudetransformer; 4 is magnetic field; and 5 is spray gun.

DETAILED DESCRIPTION OF THE EMBODIMENTS Embodiment 1 Preparing ParticleReinforced Al Matrix Composite Material (Al₃Zr_((s))+ZrB_(2(s))) inCoupling High-Power Pulse Magnetic Field and Ultrasonic Field

Raw material: metal matrix: pure Al; reaction salt: K₂ZrF₆+KBF₄ power,refined deaerating agent and slag skimming agent.

The preparation comprises two steps:

(1) Melting metal and preparing powder:

Melting 50 g of pure Al in a 60 kW resistance furnace till thetemperature raises to 900° C., and then carrying out deaeration and slagskimming Fully drying the reagents at 250° C.-300° C., in whichK₂ZrF₆+KBF₄ is ground into fine powder (particle size is less than 200mesh) and packaged by an aluminum foil for use after weighing, and theweight of the added K₂ZrF₆+KBF₄ powder being 20 percents of the weightof metal.

(2) Synthesizing composite material melt by in-situ reaction:

Refined metal liquid in accordance with reaction starting temperature(900° C.), compressing K₂ZrF₆+KBF₄ into aluminum liquid in a melt pot bya bell jar, putting the melt pot into high-power pulse magnetic field,then turning on the high-power pulse magnetic field with chargingvoltage of 1 kV and pulse frequency of 1 Hz; next, inserting anultrasonic amplitude transformer into the aluminum liquid by the depthof about 3 mm, turning on an ultrasonic device with ultrasonic fieldfrequency of 20 kHz and ultrasonic intensity of 2 kW/m², and ultrasonictreatment time being 5 minutes; after ultrasonic treatment, continuallyexerting high-frequency magnetic field for 3 minutes, then turning offmagnetic field power, keeping the melt stand until temperature falls to720° C., and casting the melt into a water-cooled copper mould with thediameter of 200 mm to obtain a composite material cast ingot.

Composite material melt has good fluidity, the obtained compositematerial casting billet has smooth outer surface, dense interiormicrostructure, and no defects of solidification structure such asporosity, shrinkage cavities, etc., and the size of particle is 0.2-0.6nm (FIG. 3).

Embodiment 2 Preparing Particle Reinforced Al Matrix Composite Material(Al₃Zr_((s))+ZrB_(2(s))) in Coupling High-Frequency Oscillating MagneticField and Ultrasonic Field

Raw material: metal matrix: pure Al; reaction salt: K₂ZrF₆+KBF₄ power,refined deaerating agent and slag skimming agent.

The preparation comprises two steps:

(1) Melting metal and preparing powder:

Melting 50 Kg of pure Al in a 60 kW resistance furnace till thetemperature raises to 900° C., and then carrying out deaeration and slagskimming; fully drying the reagents at 250° C.-300° C., in whichK₂ZrF₆+KBF₄ is ground into fine powder (particle size is less than 200mesh) and put into an injecting pot after weighing, and the weight ofthe added K₂ZrF₆+KBF₄ powder being 20 percents of the weight of metal.

(2) Synthesizing composite material melt by in-situ reaction:

A device as shown in FIG. 2, pouring refined metal liquid in accordancewith requirement of starting temperature (900° C.) into athermal-insulated composite material bath 1 from a metal refiningthermal-insulating furnace, spraying K₂ZrF₆+KBF₄ powder into the bath 1by an Ar gas spray gun 5, after spraying powder, turning onhigh-frequency oscillating magnetic field 4 with high-frequencyreference wave frequency of 20 kHz, maximum current of 80 A andoscillating wave frequency of 25 Hz, and the waveform of oscillatingwave is sine wave; next, inserting an ultrasonic amplitude transformer 3into a bath by the depth of about 5 mm, turning on an ultrasonic devicewith ultrasonic field frequency of 20 kHz and ultrasonic intensity of 10kW/m², and ultrasonic treatment time being 5 minutes; after ultrasonictreatment, continually exerting high-frequency magnetic field for 3minutes, then turning off magnetic field power, keeping the melt standuntil temperature falls to 730° C., deslagging, and casting a roundbillet with diameter of 200 mm by semi-continuous casting at 720° C.

Composite material melt has good fluidity, the obtained compositematerial casting billet has smooth outer surface, dense interior tissue,and no defects of loose and shrinkage cavities in frozen tissue, and thesize of particle is 1-5 nm (FIG. 4).

Embodiment 3 Preparing Particle Reinforced Al Matrix Composite Material(Al₃Zr_((s))+Al₂O_(3(s))) in coupling low-frequency stirring magneticfield and ultrasonic field

Raw material: metal matrix: pure Al; solid powder: industrial zirconiumcarbonate (Zr(CO₃)₂) power, refined deaerating agent and slag skimmingagent.

The preparation comprises two steps:

(1) Melting metal and preparing powder:

Melting 50 Kg of pure Al in a 60 kW resistance furnace till thetemperature raises to 900° C., and then carrying out deaeration and slagskimming; fully drying the reagents at 250° C.-300° C., in which(Zr(CO₃)₂) is ground into fine powder (particle size is less than 200mesh) and put into an injecting pot, and the weight of the added(Zr(CO₃)₂) powder being 20 percents of the weight of metal.

(2) Synthesizing composite material melt by in-situ reaction:

Pouring refined metal liquid in accordance with requirement of reactionstarting temperature (900° C.) into a thermal-insulated compositematerial bath 3 from a metal refining thermal-insulating furnace,spraying (Zr(CO₃)₂) powder into the bath by an Ar gas spray gun, turningon low-frequency stirring magnetic field with electromagnetic parameterof 10 kHz and current of 280 A; after spraying powder, inserting anultrasonic amplitude transformer into the bath by the depth of about 5mm, turning on an ultrasonic device with ultrasonic field frequency of20 kHz and ultrasonic intensity of 10 kW/m², and ultrasonic treatmenttime being 5 minutes; after ultrasonic treatment, continually stirringfor 3 minutes, keeping the melt stand until temperature falls to 730°C., deslagging, and casting a composite round billet with diameter of200 mm by semi-continuous casting at 720° C.

Composite material melt has good fluidity, the obtained compositematerial casting billet has smooth outer surface, dense interior tissue,and no defects of loose and shrinkage cavities in frozen tissue, thesize of particle is 1-5 μm (FIG. 5).

1-7. (canceled)
 8. A method of synthesizing metal matrix in-situcomposite material by coupling a magnetic field and an ultrasonic field,comprising the steps of: a) adjusting a metal-base melt to an onsetreaction temperature after refining; b) adding reactants which generatea particle phase by an in-situ synthesis reaction with the metal basemelt; c) allowing the reacted metal-base melt to stand until it iscooled to a proper casting temperature after the in-situ synthesisreaction; and d) casting the metal-base melt; wherein by simultaneouslyexerting the magnetic field and the ultrasonic field during the reactionto realize synthesizing an in situ particle reinforced metal matrixcomposite material by coupling the magnetic field and the ultrasonicfield.
 9. The method of preparing metal matrix in-situ compositematerial by coupling a magnetic field and an ultrasonic field accordingto claim 8, wherein the magnetic field and the ultrasonic field aresimultaneously exerted during the reaction in a manner of: a) preparingthe composite material melt in a bath made of thermal-insulatingrefractory material; b) inserting a high-energy ultrasonic amplitudetransformer into the upper part of the bath ; c) carrying out theultrasonic treatment to the melt; and d) exerting the magnetic field onthe outer side of the bath .
 10. The method of preparing metal matrixcomposite material by coupling a magnetic field and an ultrasonic fieldaccording to claim 9, wherein further steps comprise: a) adjusting themetal-base melt to the onset reaction temperature after refining; b)adding a reactant powder which generates a reinforced particle phase byan in-situ synthesis reaction with the metal base melt; c) turning onthe magnetic field; d) inserting the ultrasonic amplitude transformerbelow the reinforced particle phase liquid level about 5-6 mm after themagnetic field is stable, e) turning on an ultrasonic device; f)treating the reinforced particle phase ultrasonically for approximately60 s-600 s; g) turning off the ultrasonic device after the appropriateamount of time, h) turning off the magnetic field; i) allowing themetal-base melt to stand until it is cooled to the casting temperature;and j) casting the metal-base melt.
 11. The method of preparing metalmatrix in-situ composite material by coupling a magnetic field and anultrasonic field according to claim 8, wherein, the magnetic field canbe a high-power pulse magnetic filed, a high-frequency oscillatingmagnetic field or a low-frequency alternating magnetic field.
 12. Themethod of preparing metal matrix composite material by coupling amagnetic field and an ultrasonic field according to claim 11, whereinthe composite material is prepared by coupling the high-power pulsemagnetic field and the high-energy ultrasonic field, under a range ofelectromagnetic parameters of the high-power pulse magnetic field asfollows: a) a pulse current frequency approximately 0.1 Hz-10 Hz; b) apulse current density approximately 1 KA/m²-10 KA/m²; c) a chargingvoltage approximately 1 kV-20 kV; d) a central magnetic field intensityof a coil approximately 0.5-20 T; and a range of electromagneticparameters of the high-energy ultrasonic field are as follows: a) afrequency approximately 10 kHz-30 kHz, and b) an intensity approximately0.5 kW/m²-60 kW/m².
 13. The method of preparing metal matrix compositematerial by coupling a magnetic field and an ultrasonic field accordingto claim 11, wherein the composite material is prepared by coupling thehigh-frequency oscillating magnetic field and the high-energy ultrasonicfield under a range of electromagnetic parameters of the high-frequencyoscillating magnetic field is as follows: a) a high-frequency referencewave frequency approximately 10 kHz-30 kHz; b) an amplitude modulationoscillating wave frequency approximately 1 Hz-30 Hz; c) a power rangeapproximately 0-100 kW; and a range of electromagnetic parameters of thehigh-energy ultrasonic field as follows: a) a frequency approximately 10kHz-30 kHz; and b) an intensity approximately 0.5 kW/m²-60 kW/m². 14.The method of preparing metal matrix composite material in coupling amagnetic field and an ultrasonic field according to claim 11, whereinthe composite material is prepared by coupling the low-frequencyalternating magnetic field and the high-energy ultrasonic field, under arange of electromagnetic parameters of the low-frequency alternatingmagnetic field as follows: a) a frequency of approximately 0.1 Hz-60 Hz,b) a working current of approximately 1 A-10000 A; and a range ofelectromagnetic parameters of the high-energy ultrasonic field asfollows: a) a frequency of approximately 10 kHz-30 kHz; and b) anintensity of approximately 0.5 kW/m²-60 kW/m².